The present invention relates to a caliper assembly for a grinder, and more particularly to a caliper assembly including a workpiece surface inspecting device that can be maintained at a constant distance from the workpiece surface.
In a conventional grinder, such as those disclosed in U.S. Pat. Nos. 3,391,497; 4,807,400 and 4,811,524, a substantially cylindrical workpiece to be ground is held in a headstock and tailstock so that a grinding wheel can contact the surface of the workpiece. After the workpiece has been positioned in the grinder, a pair of spaced apart, workpiece measuring caliper arms are moved from their non-measuring position away from the workpiece into their measuring positions at opposite locations around the workpiece. The workpiece measuring caliper arms are moved, usually simultaneously, possibly by a single lead screw assembly or by individual controls to each caliper arm, into the measuring position. The caliper arms measure a dimension of the workpiece, such as a diameter of the generally circular workpiece. Each caliper arm has a probe which contacts the surface of the workpiece and signals when such contact occurs. Then, a dimension of the workpiece, such as a diameter, is measured by calculating a distance between the two distance measuring devices on the caliper arms.
The caliper assembly disclosed in the latter two patents also includes devices for inspecting for structural defects and surface roughness the same region along the workpiece surface at which the dimension is being measured. This inspection is performed while the workpiece surface is being measured and while the grinding occurs. The workpiece surface inspecting devices are typically contactless measuring instruments, which do not contact the workpiece and thus make their inspections from a distance away from the workpiece. In the above prior patents, the inspecting devices are located on an independent telescoping member or arm which is attached to a frame that carries the caliper arms so that the surface inspecting devices are located between the two caliper arms. The telescoping member moves the surface inspecting devices toward the surface of the cylindrical workpiece to a preset surface inspecting position which likely remains constant during the inspections.
The location and fixed measuring position of conventional surface inspecting devices have several disadvantages. They are not fixed to a measurement transducer system so that the operator would not know how near to or far away from the workpiece surface the surface inspection devices are positioned. The initial fixed position of the surface inspecting devices during the inspecting process causes the spacing between the surface inspecting devices and the workpiece surface to vary according to machine tolerances, workpiece surface variations and accuracy of the mounting of the workpiece in the grinder. Unless each workpiece is mounted in the exact same position on the headstock and tailstock of the grinder, variations in the distance between the surface inspecting devices and the workpiece surface will occur.
Variations in the distance between the surface inspecting devices and the workpiece surface can cause surfaces of different workpieces to be inspected differently, which produces erroneous readings. Thus, the conventionally mounted workpiece surface inspecting devices are unable to accurately inspect a workpiece surface.